1. Field of the Invention
The invention concerns an implantable apparatus for dosed administration of liquid medicines into the human body, comprising a housing having at least one chamber for storing the medicine, an inlet aperture in the housing sealed by means of a perforatable septum and flow-connected with the chamber, an outflow aperture in the housing, a catheter tube joined to the outflow aperture, and a particle retention device in the area of the outflow aperture.
2. Description of Background Technology
Implantable infusion arrangements or infusion ports are known, wherein the implantation location and the administration location are separate from each other. These ports conventionally consist of a medicine reservoir implanted under the skin and comprising a housing with a perforatable septum. A catheter tube extends from an outflow aperture provided in the housing, whereby the other end of said catheter tube is connected to the administration location.
Known implantable infusion arrangements therefore differ from conventional catheters, in that there is no permanent perforation of the skin in such known arrangements. Such implantable infusion devices, with which a bolus is administered, are known from, for example, DE-PS 26 26 348 (May 31, 1979) and its counterpart U.S. Pat. No. 4,140,122 (Feb. 20, 1979), DE-OS 35 18 841 (Nov. 27, 1986) and EP 134,745 (Mar. 20, 1985).
Furthermore, implantable infusion pumps are known, having constructions corresponding substantially to that of the implantable infusion arrangements described above. These infusion pumps comprise a pumping device which evenly pumps the liquid medicine provided in the reservoir through the catheter. The reservoir chamber is usually separated by means of a gas impermeable flexible wall from a further chamber with an isobar expanding pumping means. Such infusion pumps are known from, for example, U.S. Pat. Nos. 4,496,343 (Jan. 29, 1985) and 3,731,681 (May 8, 1973), DE-PS 26 04 113 (Mar. 25, 1982) and its counterpart U.S. Pat. No. 3,951,147 (Apr. 20, 1976), DE-PS 39 15 251 (Feb. 11, 1993) and its counterpart U.S. Pat. No. 5,085,656 (Feb. 4, 1992) and AT-PS 1631/88 (Apr. 15, 1990) and its counterpart U.S. Pat. No. 4,969,873 (Nov. 13, 1990).
In addition to a chamber which is continuously subject to pump pressure and dispenses the stored medicine through a capillary acting as a flow-regulating medium, such infusion pumps may also comprise a further chamber having a further injection aperture sealed by a septum, whereby the chamber is also connected with the outflow aperture, but not subject to pump pressure. An apparatus of this type is known, e.g., from U.S. Pat. No. 4,496,343 and DE-PS 39 15 251.
The infusion apparatus is implanted in a predetermined location under the skin. For the purpose of infusion, a hollow needle (cannula) pierces the skin and the septum of the infusion apparatus positioned underneath the skin. Consequently, there is a danger of skin, tissue or septurn particles being punched out or otherwise introduced into the cavity of the infusion port and that the outflow aperture and the catheter will become clogged by such particles. A variety of more or less expensive filter arrangements has been proposed to avoid such clogging by particles. Such filter arrangements are mentioned in the above-identified patent publications and usually consist of several parts, which must be mutually sealed. As a result, the installation of such filter arrangements is expensive. A filter arrangement is also known from the U.S. Pat. No. 5,108,377 (Apr. 28, 1992) wherein an outlet is integrated with a filter arrangement, resulting in a complicated structural member.